Meaning of Jacobson's organ

Ja'cob•son's or'gan

Pronunciation: ( jā'kub-sunz), [key]
— Anat., Zool. Anat.,Zool.
  1. either of a pair of blind, tubular, olfactory sacs in the roof of the mouth, vestigial in humans but well-developed in many animals, esp. reptiles.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.